1. Field of the Invention
The present invention relates to a method of preparing window glass with a gasket suitably used for window glass for automobiles and buildings, and a shaping mold used for preparing such window glass with a gasket.
2. Description of the Related Art
There have been practiced to attach a gasket or a mole (hereinafter, referred to as a gasket), which is a shaped product of rubber, elastomer or a synthetic resin, in order to apply a decorative trim strip or a seal at a glass sheet for windows of a vehicle such as an automobile or a building.
In attaching the gasket to the window glass, there have been known to use such a method that a gasket previously shaped by an extrusion process is bonded to a peripheral portion of the window glass or is fitted thereto. However, such method requires a number of working steps and much labor, and therefore it is not economical.
In order to solve the above-mentioned problems, there has been proposed a method of preparing window glass with a gasket by forming the gasket integrally with a peripheral portion of the window glass. An example of this method will be described with reference to FIG. 5.
A glass sheet 1 to be fitted to a window is placed in a shaping mold 2 so that the glass sheet 1 is interposed between upper and lower mold parts 3, 4, whereby a gasket forming cavity 5 is formed by the inner surfaces of the upper and lower mold parts 3, 4 and the outer peripheral portion of the glass sheet 1. Resilient sealing members 6, 7 are respectively disposed at portions where the upper and lower mold parts 3, 4 and the surfaces of the glass sheet 1 are in contact, in order to seal the surfaces of the glass sheet 1. Then, a gasket material such as a molten product of rubber, elastomer or a synthetic resin, or a mixture of materials capable of forming rubber, elastomer or a synthetic resin is injected into the cavity 5 followed by solidifying the gasket material, whereby the gasket is formed at a peripheral portion of the glass sheet 1 in one piece. Then, the upper and lower mold parts 3, 4 are separated from each other and the glass sheet to which the gasket is firmly attached is removed from the shaping mold 2. The above-mentioned method of preparing the window glass with a gasket is disclosed in, for instance, U.S. Pat. Nos. 4,761,916, 4,561,625, 4,584,155, 4,626,185, 4,688,752 and Japanese Unexamined Patent Publication 158481/1982.
In the conventional method of preparing the window glass with a gasket, however, the resilient sealing member is deformed due to a pressure of injection when the gasket material is injected and a space is produced between the shaping mold and the resilient sealing member. When the injected material enters in the space and solidifies in it, burrs are resulted and they deteriorate the outer appearance of the molded product, and it is difficult to remove the molded product from the shaping mold, or the apparent elasticity of the resilient sealing member becomes hard with the result of reducing the glass sheet cracking prevention effect.
In order to prevent the injected material from entering in the space between the resilient sealing member and the shaping mold when the gasket is molded, there is proposed to use a relatively hard resilient sealing member which is not deformed by a pressure of injection, or to strongly push the resilient sealing member to the shaping mold. However, either of these methods makes the resilient sealing member substantially hard whereby flexibility in the sealing member is lost. As a result, a stress is apt to gather at the glass sheet 1 owing to the lack of uniformity in shape of the shaping mold 2, the resilient sealing members 6, 7 and the glass sheet 1, so that the glass sheet 1 placed in the shaping mold 2 is easily broken. The breakage of the glass sheet is in particular apt to occur in a case that the glass sheet 1 has a complicated bent portion, or has a deeply bent portion (such as a small radius curvature or a large bending angle). Further, accuracy in the radius of curvature of the glass sheet 1 having been subjected to bending operations is sometimes insufficient. The lack of uniformity in shape of the glass sheet 1 results in breakage of it. When a sheet of window glass is not flat, namely, it is deeply bent, it is sometime difficult to seal the window glass by means of a resilient sealing member. For instance, when a sheet of window glass is a flat glass plate as shown in FIG. 5, the directions of force by the resilient sealing members 6, 7 against the surfaces of the glass sheet 1 are the same as the direction of assembling the upper and lower mold parts 3, 4 (mold-fastening directions). Namely, the resilient sealing members 6, 7 are respectively pushed to the surfaces of the glass sheet 1 by a mold-fastening pressure. However, when a glass sheet deeply bent is used, it is not always that the direction of the mold-fastening pressure is identical with the direction of forcing the resilient sealing member to the surface of the glass sheet. Accordingly, when the direction of the mold-fastening pressure is not the same as the direction of forcing the resilient sealing member, sealing effect by the resilient sealing member is insufficient, whereby leakage of the gasket material injected in the gasket forming cavity is easily caused.